The present invention relates to the ship building industry, and to multi-hull vessels equipped with hydrofoils in particular.
Catamaran vessels have good speed characteristics due to optimum hydrodynamic shape of the hull, geometrical dimensions relationship, and most importantly, the length of the hull ##EQU1## where L=length between perpendiculars, B=beam athwart ship of a hull on constructive waterline (CWL).
Maximum speed of these vessels in still water corresponds to relative speed ##EQU2## where V=speed, knots; V=volume displacement.
Relative length of high speed catamaran vessels is .lambda.&gt;10-12. Hulls are separate with a distance between them not less than the beam of the hull, which makes it possible to avoid negative interference of hulls' wave systems.
However, such vessels have low seaworthiness in rough seas due to considerable amplitudes of pitching and vertical rocking, causing shock overloads.
Increase in seaworthiness is possible by using constructive peculiarities of catamarans, placing between their hulls hydrofoil-stabilizers, the most simple and effective ones of which are shallow-submergence hydrofoils.
The application of low hydrofoils (patented in U.K. in 1968) is known and also of system comprising bow and stern hydrofoils used for stabilization of two-hull catamaran pitching (A. N. Kholodilin, A. N. Shmyreva. Vessels Seaworthiness and Stabilization in Rough Sea. Moscow, Sudostroenie, 1976, pp. 305-306).
In all cases mentioned, the use of a bow hydrofoil and a system of two bow and stern hydrofoils leads to low stabilizing effect in comparison, and barely increases the seaworthiness of a vessel.
A known catamaran has two hulls which are symmetric or asymmetric along their own longitudinal plane, and connect to each other by a deck. Mounted between the hulls are hydrofoils, one of which is the main relieving hydrofoil located near the center of mass, and the other two are trim hydrofoils located astern. The summary lift of hydrofoils is applied to the point near the catamaran center of mass, and the main relieving hydrofoil projection area is 3-5 fold more than the summary projection area of all trim hydrofoils (A. N. Kholodilin, A. N. Shmyreva. Vessels Seaworthiness and Stabilization in Rough Sea. Moscow, Sudostroenie, 1976, pp. 305-306).
A drawback of this catamaran is that when sailing in the basic mode, lift reaches a maximum value and the hulls' stabilizing properties lead to on-course unstable sailing of the catamaran. Because of the slight decrease in rolling, pitching and vertical rocking considerable shock overloads arise, especially in very rough sea conditions.
One known catamaran has two hulls which are symmetric or asymmetric along their own longitudinal plane and connected to each other by a deck, and mounted between the hulls three and more hydrofoils fastened transverse to the hulls below the waterline, and two of them are trim hydrofoils located above and astern, and the middle relieving or a group of middle relieving hydrofoils are located between the bow and stern trim hydrofoils, with summary lift arising out all hydrofoils under the sailing at maximum speed in still water at less than full weight.
This system of hydrofoils makes it possible to decrease water resistance sailing and increase the distance between the water level and lower part of the deck, and this to exclude the possibility of water flooding over the deck (U.S. Pat. No. 4,606,291, issued Aug. 19, 1986).
However, this catamaran also has low seaworthiness. As a result, high speed sailing in still water is considerably lower. Insufficient decrease of amplitude of rolling, pitching and vertical rocking leads to shock overloads arising under very rough sea conditions.
The present invention seeks to increase sailing and seaworthiness and decrease shock overloads when sailing in rough sea conditions by lessening the amplitude of rolling, pitching and vertical rocking.